Field of the Invention
The disclosure generally relates to valves. Specifically, the disclosure relates to solenoid operated valves.
Description of the Related Art
In many solenoid valve applications, especially industrial and commercial applications, a solenoid valve is required to operate over a wide range of temperatures. The mechanical performance of the valve can be affected significantly, for example, by low temperature operation that increases the amount of power required to operate the valve due to changes in the properties of mechanical components. Additionally, as a valve proceeds through its life cycle, the properties of many of the mechanical components age, causing the required mechanical force to increase and more electrical coil power to operate. In the design of such a valve, one skilled in the art generally would make an evaluation of the worst case conditions and then design the winding of the coil to a power level to accommodate the worst case. This of course will lead to a power consumption of the device that will be excessive as compared to the more normal conditions of operation.
Various known patents and applications describe measuring and affecting solenoid coil responses are known. For example, Canadian Publ. No. 2221667 teaches a proportional valve where different currents result in different positions of the internal valve spool. CA '667 seeks to more precisely maintain the position of the valve spool by sensing the temperature in an oil inlet of the valve and indirectly the temperature of the coil which affects the coils' resistance. A controller adjusts the voltage to the coil based on the variance in resistance, so that a constant current through the coil is achieved to keep a constant force on the valve spool. U.S. Pat. No. 8,681,468 teaches a method of a solenoid valve control that discloses measuring voltage across the solenoid valve coil and current through the solenoid valve coil to control the valve, such as when actual engagement of the solenoid valve occurs. US '468 teaches a reactive system that measures and monitors the current and voltage on an ongoing basis and makes adjustments based on performance of the valve, such as the timing, to lessen overpowering of the valve. US Publication No. 2014/0222313A1 teaches a method of energizing a solenoid valve of a hydraulic control system according to a predetermined timing schedule to move a valve member of the solenoid valve connected to a switching component to deliver pressurized fluid when the valve member moves to switch a switching component. An operating parameter is measured and may be a period of time over which the valve member moves, or a sensed operating parameter of the fluid, such as pressure or temperature. The measured parameter is then compared with a predetermined parameter, and energizing of the solenoid valve is then adjusted based on the difference.
However, these patents and applications apparently disclose systems and method that have not been generally implemented in the industry, possibly due to complexity, longevity, and costs. In many instances, especially for solenoids operating directional control valves that are switching on and off and not proportionally controlled to variable positions, the control systems monitor changes in resistance from the operational heating of the coil and adjust the voltage or duty cycle to generate a constant current for the solenoid valve to actuate with the assumption that the same current will produce the same results in actuation.
There remains a need for a control system for a solenoid valve under various environmental operating conditions independent of a need for constant monitoring of the solenoid valve that is simple and inexpensive, and can be widely adapted in the field.